1. Field of the Invention
The present invention relates generally to tools used in fabrication of nuclear reactor core component rods and/or fuel rods and, more particularly, is concerned with a hand-actuated tool operable for inserting and releasing a spring clip at a desired axial position in a tube of a core component or fuel rod.
2. Description of the Prior Art
A nuclear reactor core is composed of a large number of nuclear fuel assemblies arranged in side-by-side relationship. Each fuel assembly includes a plurality of fuel rods held in a stationary array by a skeleton of the fuel assembly. The fuel assembly skeleton is composed of a plurality of control rod guide thimbles disposed between and extending parallel to the fuel rods, a plurality of grids mounted to and axially spaced along the guide thimbles and supporting the array of fuel rods, and top and bottom nozzles dispose adjacent to and attached at opposite ends of the guide thimbles. Each fuel rod includes an outer hollow tube sealed by end plugs attached to opposite ends of the tube and a plurality of fuel pellets disposed in stacked relation within the tube.
In addition to fuel rods, typically some of the nuclear fuel assemblies also include core component rods, such as control rods, secondary source rods, and burnable poison rods. Control rods are reciprocally movable within the guide thimbles of the fuel assemblies to control the fission process over the life of the fuel assembly. Secondary source rods and burnable poison rods are mounted in removable subassemblies which can be inserted into selected fuel assemblies. Secondary source rods have internal components, such as highly enriched material, which provide additional reactivity to facilitate start-up. Burnable poison rods have internal components, such as neutron absorbing material, which function to enhance distribution of fuel during burnup.
Core component rods have outer tubes which contain the internal components and are sealed by end plugs connected to opposite ends of the tubes. The internal components thermally expand during operation of the reactor core and thus empty space must be initially provided in the outer tubes between the internal components and end plugs.
It is desirable to provide some type of mechanical restraint or retention device, such as a C-shaped spring clip, within the tubes to retain the internal components in "as-loaded" locations and prevent their movement during shipping and handling. The uncompressed spring clip has a diameter larger than the inside diameter of the tube of the core component rod so that after the spring clip is installed it bears against the inner wall of the tube, thereby resisting axial sliding loads of the internal components. Proper installation of the C-shaped spring clip involves, first, partially compressing the clip to a diameter less than that of the tube; then, inserting the compressed clip into the tube to the desired location; and, finally, releasing the clip at the desired location in the tube. The desired axial location of the spring clip inside the tube varies greatly from one core component rod design to another.
Prior art tools to facilitate the insertion and release of a spring clip in a core component rod tube are described in U.S. Pat. No. 4,514,889 to Ferlan et al which is assigned to the assignee of the present invention. While these tools represented steps in the right direction, they have certain disadvantages in design and use in terms of their bulkiness and excessive weight, difficulty of insertion and manipulation, inability to actuate with one hand in a "natural" position while maintaining the tools in proper alignment with the rod tube, lack of means to tell if the clip is in proper axial position prior to actuation to release the clip, and inherent potential for damaging the rod tube.
Consequently, there is a need for a spring clip insertion tool having an improved design that will overcome the above-described disadvantages.